Children commonly play with toys or games of type employing a substantially planar play surface, such as, for example, checkers, drawing boards, chessboards, etc. Certain building block toys which detachably snap together by virtue of complementary mating features, e.g., Lego.RTM.-type building block toys, may also be used with substantially planar sheet members carrying the characteristic mating features on one side of the sheet for attachment to loose blocks.